Catalytic naphtha reforming with a platinum-alumina catalyst



J. WEIKART CATALYTIC NAPHTHA REFORMING WITH A PLATINUM-ALUMINA CATALYSTFiled July 19, 1952 mw 3 MN snventor Jo h n (4151 Kart United StatesPatent CATALYTIC NAPHTHA REFORMING WITH A PLATINUM-ALUMINA CATALYST JohnWeikart, Westfield, N. J., assignor to Esso Research and EngineeringCompany, a corporation of Delaware Application July 19, 1952, Serial No.299,826

3 Claims. (Cl. 196-50) The present invention relates to improvements inthe hydroforming of naphthas conducted in the presence of a noble metalsuch as platinum or palladium. More particularly, the invention relatesto a method of regenerating the catalyst with an oxygen-containing gasunder conditions more fully set forth hereinafter.

Hydro'forrning of naphthene-containing naphthas in the presence of aplatinum is a matter of record and commercial practice with respect tofixed bed type of operation. in the prior practice, the hydroformingoperation is carried out at very high pressures, namely, 'of the orderof 590 p. s. i. or higher in the so-called non-regenerative type ofoperation. in this latter type of operation, the hydrogen partialpressure in the reaction zone is maintained at such a hi h degree thatthe tendency of carbonaceous deposits to accumulate on the catalyst isrepressed, and according to the patents and literature on the subject,the operation may be carried out continuously for an extended period oftime without requiring interruption of the process to regenerate thecatalyst.

Operating the hydroforming operation in the presence of a noble metal atvery high pressures not only is an expensive operation from thestandpoint of equipment, such as compressors and reactors which willWithstand such pressures at high temperatures, but has the furtherdrawback that the quality of the product is not as high as can beobtained at lower operating pressures.

it has been proposed to operate a hydroforrning process using noblemetal catalyst under somewhat lower pressures than those indicatedabove. This operation at lower pressures results in the deposition ofcarbonaceous material on the catalyst so that it requires periodicregeneration with hydrogen to restore its activity. Hydrogenregeneration of a platinum catalyst has not proven very successfulunless the catalyst was regenerated at frequent intervals, or in otherwords, after it had been in the on-s'tream operation for a relativelyshort period of time.

The present invention relates to a process of carrying out thehydroforming of naphthas in the presence of a platinum group metalcatalyst while the catalyst is in the form of a dense fluidized bed atrelatively low pressures, say, of the order of about 200 p. s. i.,whereupon the catalyst acquires carbonaceous deposits. According to thepresent invention, this catalyst which has been deactivated byaccumulation of carbonaceous deposits may be regenerated employing anoxygen-containing gas, under specified conditions more fully set forthhereinafter, to the extent that a small amount of carbonaceous materialremains on the catalyst.

Hydroforming may be defined or indicated as an operation in which avirgin naphtha containing a substantial amount of naphthenichydrocarbons is contacted at elevated temperature and pressure with asuitable catalyst and in the presence of added hydrogen for asuflic'ient period of time to effect the desired conversion. The mainreaction is one in which the naphthenes are dehydrogenated to thecorresponding aromatics, but in addition to that, some isomerization ofhydrocarbons, and some iatented Oct. 2, 1956 hydrocracking of paraflinsalso occurs. The boiling range of the major portion of the feed stock isnot substantially altered, although the boiling point of the formedaromatics is substantially higher than the corresponding naphthenehydrocarbons from which they are formed. The hydrocracking of theparafiins to lower boiling constituents substantially cancels out theeffect of the aromatizationof the naphthenes to raise the boiling range.Under properly conducted operation, the process results in the formationof a 10 pound Reid vapor pressure gasoline in yields better than It is acharacteristic of this hydroforming operation that there is no netconsumption of hydrogen and usually there is a net production ofhydrogen.

The main object of the present invention is to carry out thehydroforming of virgin naphthas to produce in good yields gasolineconstituents of improved octane rating, the operation being carried outin the presence of a noble metal catalyst which is in the form of adense fluidized bed, and to maintain the catalyst at a high level ofactivity and selectivity.

Another object of the present invention is to carry out the hydroformingoperation using platinum or palladium at pressures substantially lowerthan those heretofore employed whereby the quality of the productobtained is superior in that the octane value is greater.

Another object of the present invention is to regenerate the platinumcatalyst with an oxygen-containing gas.

Other and further objects will appear from the following more detaileddescription and claims.

In brief compass, the present invention relates to carrying out thehydroforming of naphthas in the presence of a noble metal catalyst of agroup consisting of platinum and palladium supported on a suitable basesuch as active alumina and also containing a minor quantity of hydrogenfluoride, in a two zone system, the first of which is a reaction zonecontaining a catalyst in the form of a dense fluidized bed, and thesecond of which is a regeneration zone also containing a catalystundergoing regeneration while in the form of a dense fluidized bed,further characterized in that the catalyst is not completelyregenerated, but rather a relatively small amount of carbonaceousmaterial is permitted to remain on the catalyst as it is returned to thereaction zone. It has been found that by so operating, the activity ofthe catalyst is maintained at a high value.

in the accompanying drawing there is shown, diagrammatically, theessential elements of an apparatus in which the present invention may becarried into effect.

Referring in detail to the drawing, 1 represents a naphtha feed linethrough which from some source not shown the naphtha to be treated isintroduced into the system. From line 1 the oil passes to a heatingmeans such as a fired coil 2 disposed in a furnace setting 3, whereuponit is heated to a temperature of about 900-925 F. The preheated andvaporized oil is withdrawn from coil 2 and thence pumped by pump 4through line 5 into reactor 6.

In the interest of heat economy, it is desirable to preheat the cold oilby heat interchange with hot products. This is not shown in the drawingbecause it is a conventional step in oil refining, generally. Ahydrogen-containing gas is also fed to reactor 6. This gas may beWithdrawn from an outside source not shown yia line 7 and chargedto acoil s disp'osed in the furnace 9. How

ever, when the process has been onstream for a period of time,sufiicient hydrogen-containing gas may be obtained from the productrecovery system, and this hydrogen-com.

3 ous hydrocarbons) is heated to a temperature of about l 00-1200 F.,thence withdrawn through line 3 and charged into the bottom of reactor6.

It is to be noted that the hot oil and hydrogen gas are not mixed priorto introduction into reactor 6. The purpose of this is to avoid possiblethermal cracking of the oil by contact with the hydrogen in the transferlines.

The hydrogen-containing gas introduced into reactor 6 passes upwardlythrough a foraminous member G and thence into the bed of catalyst Cwhich, as stated previously, is in the form of a dense fluidized mass,which dense fluidized mass has an upper level L. The velocity of thegaseous material, that is, the oil and the hydrogencontaining gas andother gaseous constituents, is controlled within the limits of fromabout .1-2 feet per second so as to form the dense fluidized massreferred to. To accommodate this result, of course, the catalyst musthave the proper particle size, namely, it should have a particle size offrom 0-200 microns, and with over 50% of the catalyst having a particlesize of from about 40-80 microns. As to particle size, good results fromthe standpoint of fluidizable catalyst are obtained when the catalysthas a particle size distribution Within the following ranges:

Weight per cent 0-20 microns -10 20-40 microns 20-30 40-80 microns 60-7030-200 microns 10-15 Under the conditions more fully set forthhereinafter,

the desired reaction occurs and the raw product is withdrawn fromreactor 6 overhead via line 11. The space between L and the top of thereactor is occupied by a dilute suspension of catalyst in gasiforrnmaterial, the concentration of which decreases upwardly. It is thepurpose of this type of operation to effect a separation of the mainbulk of the catalyst within the reactor itself, and this is accomplishedby providing the disengaging space in the reactor above L. However, toremove entrained catalyst which still is contained in the gasiformmaterial about to emerge in the reactor, the gasiform material is forcedthrough one or more cyclones S wherein these fines are separated andreturned to the dense phase via dip pipes d. The raw product in line 11may still contain entrained catalyst, and if so, may be charged into ascrubber 12 where it is passed countercurrently upward against feed oil,for example, introduced to the top of the scrubber through line 13. Thisscrubbing oil which is cold causes a partial condensation of thenormally liquid constituents, and the feed oil and the condensate servesto remove the last traces of the catalyst in the form of a slurry, whichmay be withdrawn through line 14 and charged to the bed of catalyst C.The vaporous material is withdrawn from scrubber 12 through line 34 andpassed into a separator 15 wherein hydrogen-containing gas is separatedand recycled via line 10 to coil 8 for further use in the process. Aportion of this gas may be rejected from the system through line 16. Thecrude product substantially freed from hydrogen is then withdrawn fromseparator 15 through line 35, thence passed through pressure reducingvalve 17, thence passed via line 18 into a second separator 19. Fromseparator 19, normally gaseous constituents, such as methane, ethane andthe like, may be withdrawn overhead through line 20 and utilized in anyconventional manner for which they are suitable. These gases in line 20mainly consist of methane and ethane. The desired product is withdrawnfrom separator 18 through line 21 and passed to a finishing still 22from which the desired product is recovered overhead through line 23 gastaps t.

and collected in a receiving drum 24. Heavy polymer is withdrawn fromthe bottom of still 22 through line 25, and this material may be eitherrejected from the system or recycled to line 1 for further treatment.This heavy polymer ordinarily does not amount to more than 2% of thetotal liquid product.

The catalyst in reactor 6 acquires carbonaceous deposits, particularly,at the low pressures here utilized. Consequently, it will requireregeneration. According to the present invention, the regeneration iscarried out utilizing air. To this end, the catalyst is withdrawn fromreactor 6 via standpipe 26 provided with the usual Through these gastaps a small amount of gas may be injected into the standpipe to preventbridging, clogging and to otherwise improve the fluidity of thedownflowing catalyst. This gas may be some of the recycled gas obtainedfrom line 10. The flow of catalyst in standpipe 26 is controlled byvalve 27. The thus withdrawn catalyst is discharged into line 28containing a stream of air, and the catalyst is picked up by the air andformed into a suspension and carried into the bottom of regenerator 29.

This regenerator is similar in construction to reactor 6 being providedwith gas distributing means G1. Furthermore, the gas velocities invessel 29 are controlled within about the same limits as those describedas prevailing in reactor 6 whereupon a second fluidized bed of catalystC1 is formed in the regeneration vessel, which fluidized bed has anupper dense phase level at L1. The air fed to the bed of catalyst C1burns oif the carbonaceous deposits and the fumes pass from theregenerator through the disengaging space between L1 and the top of theregenerator wherein separation of the main bulk of the catalyst from thegasiform material is eifected. As in the case of reactor 6 theregenerator is provided with one or more cyclone separators S1 throughwhich the fumes are forced to separate entrained catalyst, whichseparated catalyst is returned to the dense phase via dip pipes d1. Theregeneration fumes substantially freed of entrained catalyst pass fromthe reactor via line 30. As pointed out previously, the catalyst inregenerator 29 is incompletely regenerated so that some carbonaceousmaterial remains on it. The partially regenerated catalyst is thenwithdrawn from the regenerator 29 via standpipe 31, controlled as usualby valve 32 and charged to the reactor as shown. As usual, the standpipe31 is provided with gas taps t which provide a fluidizing gas so thatthe catalyst may flow readily from the regenerator to the reactor.

In the interest of simplicity only the essentials of a suitableapparatus have been described, and those familiar with the art willappreciate that accessory apparatus would be used to improve theefficiency of the process from an engineering standpoint, thus, theskilled engineer will readily appreciate that heat exchanges, flowmeters, pressure recorders and temperature recorders etc.

would form a part of the apparatus actually used in a commercialinstallation in the interest of etficiency of operation.

In order to disclose the invention more fully, the following conditionsof hydroforrning and regeneration giving good results are set forth:

octane gasoline). Cubic feet of hydrogen fed per bbl. of 4,000-8.000 C.F./B.

oil 1(concentration of hydrogen in re- (80-95% H2); cyc e gasW/ClElI/W=lbs. .of oil per hour per 1b. of catalyst in the reactor.

Conditions in regenerator 29 Temperature 900l000 F. Pressure 150-300 p.s. i.

Poluntgs of air per 100 pounds of catas Carbon on catalyst returned toreactor" .1.5, preferably .3.5.

In order to show the beneficial effect of the partial regeneration ofcatalyst, the following data are set forth. The regeneration was carriedout on a platinum catalyst contaminated during an operation ofhydroforming in which the temperature was 900 F., 6,000 cubic feet ofhydrogen per barrel was fed with the oil to be hydroformed, the oil feedrate was 1 lb. of oil per hr. per lb. of catalyst in the reactor, andthe reaction Zone was maintained under a pressure of 200 p. s. i. In thebelow regenerations which numbered some 14, it will he noted that wherethe catalyst was partially regenerated the research octane number of thegasoline decreased in value during the onstream period following thefirst regeneration, but after that there was no further decrease in theoctane level of the product during the :onstream periods following thenext thirteen regeneration phases of the cycle. Where the catalyst wascompletely regenerated, it will be noted that the research octane numberof the product continued to decline after each catalyst regenerationphase until following the 14th regeneration phase or period, it was fourpoints lower than during the corresponding regeneration period in thecase where the catalyst was incompletely regenerated.

To recapitulate briefly, the present invention relates to improvement offluid catalyst hydroforming of naphthas conducted in the presence of aplatinum or paladium catalyst. The process is characterized in that inthe interest of improved yield octane relationship, the operation iscarried out at pressures substantially lower than those currently used,for example, in hydroforming naphthas, the conventional fixed bedoperation is conducted under pressures of 500 pounds or greater. Thistype of high pressure operation does not result in the production of ahigh octane gasoline. The lower pressures employed in the presentinvention have the advantage that the gasoline produced has an octanenumber of or higher. Furthermore, excellent yields are secured. Anotherimportant aspect of the present invention has to do with maintaining thecatalyst at a high activity level by regenerating fouled catalyst withair or other oxygen-containing gas under conditions such that arelatively small amount of carbon remains on the catalyst following theregeneration. Insofar as known, previous attempts to regenerate aplatinum type of catalyst have not met with success because after eachregeneration the catalyst suffered a severe loss in activity. It hasbeen discovered that by permitting a relatively small amount of materialto remain on the catalyst, these severe losses of activity followingregeneration with air are avoided.

Numerous modifications of the invention may be made by those skilled inthe art without departing from the spirit thereof.

Iclaim:

1. A continuous method of hydroforming naphthas in a system comprising ahydroforming Zone and a catalyst regeneration zone which comprisesfeeding a naphtha and a hydrogen-containing gas to the hydroforming zoneOriginally containing a fluidized bed of fresh powdered catalystcomprising platinum supported on active alumina, maintaining thehydroforming zone at a temperature of from 850 to 950 F., and a pressureof from to 300 p. s. i. for a sufiicient period of time to efiect thedesired conversion, withdrawing catalyst fouled during the hydroformingreaction, conducting it to a regeneration zone, treating the catalystwith an oxygen-containing gas while in the form of a dense fluidized bedin said regeneration zone until carbonaceous deposits are removed to theextent that the catalyst still contains from .3 to .5 wgt. per centcarbonaceous material, thereafter returning the hot uncooled catalyst tothe react-ion zone, repeating the above indicated cycle wherein duringeach regeneration the catalyst is returned to the reaction zonecontaining the above amount of carbonaceous material following eachregeneration and recovering from said reaction zone a product containinggasoline constituents of improved octane rating.

2. The method of claim 1 in which the oxygen-containing gas is air.

'3. The method of claim 1 in which the catalyst regeneration isconducted at temperatures above those prevailing in the hydroformingzone.

References Cited in the file of this patent UNITED STATES PATENTS2,253,486 Belchetz Aug. 19, 1941 2,410,891 Meinert et al. Nov. 12, 19462,479,110 Haensel Aug. v16, 1949 2,642,381 Dickinson June 16, 1953

1. A CONTINUOUS METHOD OF HYDROFORMING NAPHTHAS IN A SYSTEM COMPRISING AHYDROFORMING ZOEN AND A CATALYST REGENERATION ZONE WHICH COMPRISESFEEDING A NAPHTHA AND A HYDROGEN-CONTAINING GAS TO THE HYDROFORMING ZONEORIGINALLY CONTAINING A FLUIDIZED BED OF FRESH POWEDERED CATALYSTCOMPRISING PLATINUM SUPPORTED ON ACTIVE ALUMINA, MAINTAINING THEHDYROFORMING ZONE AT A TEMPERATURE OF FROM 850* TO 950* F., AND APRESSURE OF FROM 150 TO 300 P.S.I. FOR A SUFFICIENT PERIOD OF TIME TOEFFECT THE DESIRED CONVERSION, WITHDRAWING CATALYST FOULED DURING THEHYDROFORMING REACTION, CONDUCTING IT TO A REGENERATION ZONE, TREATINGTHE CATALYST WITH AN OXYGEN-CONTAINING GAS WHILE